(1) Field of the Invention
This invention relates to a display driver module and its mounting structure and, more particularly, to a display driver module having a driver integrated circuit for driving a large-screen flat panel display, such as a plasma display, and a wiring board on which this driver integrated circuit is mounted and being suitable for fixing this driver integrated circuit on a metal chassis on the flat panel display to radiate heat and a mounting structure for a portion where such a display driver module is mounted on a plasma display panel.
(2) Description of the Related Art
Attention is riveted to a large-screen flat panel display with a plasma display panel on it as the likeliest candidate for a next-generation large-size television because of its small depth, wide view angle, and easiness of making a large screen. These are the merits of an ordinary flat display.
This plasma display has a large number of driver integrated circuits for leading display signals to a plasma display panel and is controlled and driven by a display driver module which received control signals from a control board. This is the same with a display device using a liquid crystal panel, being a flat display. FIGS. 10 and 11 show the structure of such a conventional display driver module.
FIG. 10 is a perspective view showing an example of a conventional display driver module. FIG. 11 is a cross-sectional view of a feature of a conventional display driver module.
A conventional display driver module with integrated circuit chips, which generate much heat, on it uses a flexible wiring board 101 with a wiring pattern (not shown) formed on its top, to the bottom of which an aluminum plate 102 for radiating heat is attached.
A hole 103 is made at an integrated circuit chip mounting portion (die bonding portion) in the flexible wiring board 101. An integrated circuit chip 104 for a driver is attached through the hole 103 directly to the aluminum plate 102 for radiating heat by the use of an adhesive 105. An electrode on the integrated circuit chip 104 and a copper pattern for wiring on the flexible wiring board 101 are connected with a gold wire 106 by wire bonding, and then the integrated circuit chip 104 is coated with resin 107.
An input electrode portion 108 for connecting to a control board is formed at one end of the flexible wiring board 101 and an output electrode portion 109 for connecting to a plasma display panel is formed at the opposite end.
A display driver module having such a structure uses the flexible wiring board 101 with the aluminum plate 102 for radiating heat attached to it. This structure results in a high cost. Therefore, it is suggested that a metal chassis on a display should be used as a radiator for the integrated circuit chip 104.
Furthermore, the integrated circuit chip 104 for a driver and a wiring pattern on the flexible wiring board 101 are connected by wires which are stretched one by one with a wire bonder. With an increase in production, however, the productivity of such wire bonding is becoming an issue, as with liquid crystal panels ahead of plasma display panels. That is to say, if there are a large number of terminals on which wire bonding must be performed, a wire bonding process will take much time. Furthermore, many wire bonders are necessary for mass production, resulting in a high equipment investment cost. Therefore, flip chip bonding suitable for mass production is attempted.
In some examples of the flip chip connection, an anisotropic conductive resin is used as the most economical structure. It is discussed in Japanese Patent Laid-Open Publication No.Hei9-244047, Japanese Patent Laid-Open Publication No.Hei9-146110, Japanese Patent Laid-Open Publication No.Hei7-211423, etc., in which it is used primarily for a liquid crystal panel. It is also applied to a printed circuit board, of course. Japanese Patent Laid-Open Publication No.Hei11-67832 discloses such an example.
FIGS. 12(A) and (B) are fragmentary cross-sectional views showing a schematic of a mounting structure for a conventional display driver module. FIG. 12(A) is a fragmentary cross-sectional view of its feature. FIG. 12(B) is an enlarged cross-sectional view of its integrated circuit mounted portion.
With a plasma display panel, an X-side sustain circuit board for controlling and driving an X electrode on its front panel, a Y-side sustain circuit board for controlling and driving a Y electrode on its front panel, and a logic circuit board for controlling and driving an address (A) electrode on its back panel are signal processing circuits connected to it. The X-side sustain circuit board is connected to the plasma display panel via a flexible wiring board. Each of the Y-side sustain circuit board and the logic circuit board is connected to the plasma display panel via a display driver module, being a flexible wiring board with a driver integrated circuit mounted on it. Connections formed by these display driver modules and the plasma display panel have the same structure. In addition, connections formed by these display driver modules and the signal processing circuits also have the same structure. In FIG. 12, therefore, an address driver module which connects the logic circuit board and the A electrode is shown as an example.
A plasma display panel consists of a front panel 111 and aback panel 112, which are supported with an aluminum chassis 114 via an adhesive sheet 113. An address bus board 115 for connecting the aluminum chassis 114 and a logic circuit board is placed on the aluminum chassis 114. A connector 116 is placed on the address bus board 115.
An address driver module consists of an address integrated circuit 117 and a flexible wiring board 118. One wiring end of the flexible wiring board 118 is connected to the address bus board 115 by the connector 116 and the other wiring end of the flexible wiring board 118 is connected to an A electrode on the back panel 112 by an anisotropic conductive film (ACF) 119 into which conductive particles are mixed.
The address integrated circuit 117 is connected to the flexible wiring board 118 by the eutectic soldering of gold bumps 120 formed on a circuit-formed surface of the address integrated circuit 117 and tin (not shown) on copper wiring formed on the flexible wiring board 118. A portion around the connection is filled with an underfiller 121.
As stated above, in a conventional mounting structure for a display driver module, the flexible wiring board 118 and the plasma display panel are connected by the anisotropic conductive film 119 and the flexible wiring board 118 and the signal processing circuit are connected by the connector 116. An ampere-level powerful electric current which runs through a power-supply terminal of the address integrated circuit 117 must be handled. Furthermore, the address integrated circuit 117 must be replaced when it fails. If these things are taken into consideration, it is rational to use the connector 116.
Even in a conventional display driver module in which bonding time is taken into consideration, however, an integrated circuit chip with bump electrodes on it is facedown-bonded to a flexible wiring board and a joint formed by them is solidified with an underfiller. The process for connected them therefore takes much time.
Furthermore, in a mounting structure especially for a conventional scan or address display driver module, a connection at gold bumps formed by a driver integrated circuit and a flexible wiring board, in the display driver module, is filled with an underfiller, an anisotropic conductive film is used at a connection formed by the display driver module and a plasma display panel, and a connector is used at a connection formed by the display driver module and a signal processing circuit. That is to say, these three connections differ in mounting structure. This results in a complex structure and an increase in the number of the types of materials used at the connections.
In order to address such problems, the present invention was made. In other words, an object of the present invention is to provide a low-cost display driver module in which a metal chassis on a display with an integrated circuit chip mounted on it is used as a radiator for the integrated circuit chip, which shortens the process for connecting the integrated circuit chip and a wiring pattern on a flexible wiring board, and which uses the metal chassis on a display panel as a radiator.
Another object of the present invention is to provide a mounting structure for a display driver module in which the structure of connections for a scan and address driver module for a plasma display is simplified.
In order to achieve the first object, a display driver module for driving a flat panel display is provided. This display driver module comprises a flexible wiring board on which a wiring pattern is formed and one or more integrated circuit chips with bump electrodes for driving a display which have one surface the bump electrodes are formed on and the other surface fixed onto the flat panel display so as to adhere to a metal chassis on a display panel and which are bonded to the flexible wiring board by joining, with pressure applied, the bump electrodes to the wiring pattern with one film or paste selected from a group consisting of an anisotropic conductive film, an anisotropic conductive paste, a non-conductive resin paste, and a non-conductive resin film between.
Furthermore, in order to achieve the second object described above, a mounting structure for a display driver module in which a driver integrated circuit for driving a plasma display panel by receiving signals from a drive circuit board and a display driver module having a wiring board on which the driver integrated circuit is mounted are fitted on the plasma display panel is provided. In this mounting structure for a display driver module, a gap between the wiring board and the driver integrated circuit connected to the wiring board via gold projections formed on connection electrodes, in the display driver module, is filled with an insulating resin, a portion around a joint formed by a connection pad at the wiring edge of the wiring board and a connection pad on the plasma display panel at a connection formed by the display driver module and the plasma display panel is filled with the insulating resin, and a portion around a joint formed by a connection pad at the wiring edge of the wiring board and a connection pad on the drive circuit board at a connection formed by the display driver module and the drive circuit board is filled with the insulating resin.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.